Realistic metal textures
Metal materials are pure gloss and if you want it painted then 

1-It's metal that have been painted (like it's been sprayed with paint)
which is gloss shader mixed with a paint material using a mix shader and the Factor is an image texture made to tell blender where is gloss and where is paint

2-It's like metal that is factory painted
which is gloss with an image texture

note that metal has a colored rim light 

for the best realistic result look up PBR materials 

I recommend blender guru's tutorial ..2 videos that explain PBR materials the second one is about accurate metal materials but you need to see the first one